Automatic transmission-measuring set



March 27, 19286 F, H. BEST AUTOMATIC TRANSMISSION: MEASURING SET 2Sheets-Sheet 1 FiIed'M'ay $1925 29 z 0'' 0 rol l i 53 0 3653 N. 333 3 N5% j E i5 .1! E $83., I b

- INVENTOR Y EEBBSZ' ATTORNEY March 27, 1928.

.-V i F. H.,BE$T AUTOMATIC TRANSM1SION MEASURING SET Filed May 9, i925 2Sheets-Sheet 2 Fatented 4 Mar. 27, T928.

are srrs are.

ear, is

FRED H. BEST, OF XKTES'IFIEIZJI), NEW JERSEY, ASSIGNOR TO AMERICANTELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

AUTOMATIC TRANSMISSION-MEASURINGSET.

Application filed May 9, 1925. Serial No. 28,188.

This invention relates to improvements in devices forrmeasuring ortesting electrical currents.

The invention is particularly adapted for making measurements to obtainor test the transmission equivalent of telephone circuits, although itmay be utilized for other purposes. One of the cardinal features of thedevice of the invention is that its operation is entirely automatic. Itthus does away with all manually operated dial arrangements of formersystems and allows measurements and tests to be made with far greaterfacility and speed than heretofore. Further features and purposes of theinvention will appear more fully from the following detailed-description thereof. The inventionymay be more fully understood fromthe following description together with the accompanying drawing in theFigures 1 and 2 of which the invention is illustrated. Fig. 1 shows aschematic circuit arrangement oftheinvention, while in Fig. 2 is shownin detail circuit arrangements of a portion of the device.

In Fig. 1 is shown a transmission-line L whose transmission efiiciencyit is desired to obtain by measuring the transmission characteristicsthereof. The line L is shown interconnecting two stations A and B. Tomeasure the transmission characteristics of the line L a cord circuit 3at station A. would be connected to the-line and to one of a number ofmultiple jacks 2 which-are connected tov an oscillator 1. A desirablefrequency for the oscillator might in practice be 1,000 cycles. Atstation B a cord circuit 4 would connect the line L to one of a numberof contacts 5' of a selector switch. The contact arm 5 wouldautomatically find the contact and stop there. This arrangement isutilized so that only a single line may be connected to the measuringset at one time. Current from the oscillator 1 will then be transmittedfrom station A over the line L to station B and thence over conductor 6to the measuring'set. Current of the testing frequency will be impressedona circuit '7 which includes the device 8 for introduc- 50 ing a lossstep by step and the device 9' for decreasing the loss step by step. Thecurrent will then be transmitted to an amplifier rectifier device 12 andthen transmitted through the voltmeter relay 13. With the devices 8 and9 set at normal, that is, with 'ten transmission units. In other words,the

the switch 10 on its farthest left-hand contacts and with the switch 11on-its lowest contacts, the current from the oscillator 1 transmittedover the line L will operate the voltmeter relay 13 so that it willclose its contact 14. This will complete a. circuit over conductor'16 totlze stepping mechanism 18 and cause it to start operating to move theswitch 10 successively 'over its contacts; This operation will insuccessive steps add in series in the circuit the individual resistanceelements such as r and will decrease the number of resistance'elementssuch as r connected in shunt across the circuit. This will tend tointroduce a loss step by step, in the circuit and decreasethe energytransmitted thereover. It is pointed out that each step of the device 8has an arbitrary value, which in this instance, may be termed as a stepof device 8 is arranged to increase the loss in 1 steps of tentransmission units each. When the current has been decreased at certainamount by this method the voltmeter relay 13 will operate to opencontact 1 1 and to close contact 15. This operation will stop themechanism 18 and hold it in operated position. A. circuit will now beclosed over I contact 15 and conductor 17 to the stepping mechanism 19,thus starting it in operation. The mechanism 19 will move the switch 11upward stepl by step over its contacts, thus increasing t e ratio of theresistance across the amplifier inpiit to the total resistancecontrolled by the switch, thereby increasing the voltage across theamplifier input terminals. This will tend to decrease the loss step bystep, i1ntil-the current again will be just strong enough to againoperate relay 13. This will open the circuit 17 and stop the apparatus19 from operating. It will also again close circuit 16. This will nowoperate to lock all of the apparatus up. It has been pointed out thatthe apparatus 8 consisted of anumber of steps of ten transmission unitseach for increasing the loss. The apparatus 9 will, as a whole, equal orcounteract one of'these steps. Accordingly, it will be subdivided into anumber of steps, such for examplejas twenty steps each of one half atransmission unit. With such an arrangement an accurate measurement maybe made of the transmission equivalent of the line. Associated with thedevices 8 and 9 would bea signal panel, such as 20, which would indicateto the test operator the exact -number of transmission units andfraction thereof which had been cut into the line to obtain a conditionof equality. By well known methods of comparison, this would be utilizedto" indicate the transmission equivalent of the line.

In Fig. 2 there is shown in detail a circuit diagram of the measuringset heretofore illustrated schematically. Similar reference charactershave been utilized to denote like parts in all of the figures of thedrawing. The conductor 6 is shown in Fig. 2 as termimating in the plug Padapted to be connected to jack J of the measuring set. i lccordingly,

the voltage from circuit 6 will be applied to the circuit 7 of themeasuring set and will through the'receiver shunt and potentiometer, thevoltage is applied to the amplifier rectifier 12 and thence to thevoltmeter relay 13. It is pointed out that when plug Pis inserted injack J the .sleeve circuit will cause relay 21 to operate for purposesto bepointed out hereinafter. The incoming volt,-

- age will be reduced by. the potentiometer by a ten transmission unitratio and then applied to the amplifier 12 and to the voltmeter relay13. This applied voltage will cause the relay 13 to pull up and closecontact 14. This will cause the following cir cuit to be closed: fromground contacts of 'relays 26 and 27, conductor 28, contact 14,

conductor- 29, contact to relay 24, conductor 30, winding of relay 22 tobattery and ground, .thereby operating relay 22., The operation of relay22 will open at its right hand contact, a circuit 31 common to all ot'the indicating lights in the signal panel..

The operation of relay 22 also closes the following circuit: from groundcontact of relay 21, conductor'33, winding of relay 23, conductor 32,middle contact and armature of relay 22 to battery and ground. Thiswillcause relay 23to operate and to lock up over its contact. The operationof relay 22 will also close the following circuit: from ground armatureand contact of relay 22, conductor 34, contact and armature of relay 35to battery and ground. This will cause relay 35 to operateintermittently to step the selector arms of mechanism 8 around step joystep. The receiver shunt mechanism 8 accordingly will introduce into thecircuit with each stepa loss of ten transmission units. The mechanismcontinues to step until the loss introduced is such that the currentthrough the voltmeter relay 13 falls below its marginal point,thuscausing the armature of said relay to fall back and close thecontact 15. This will cause the relay 22 to release and also cause acircuit to be closed from conductor 28, contact 15, conductor 36,armature and contact of relay 23, conductor'iii', winding of relay 25 tobattery and ground, thereby causing relay 25 to operate. It opens at itscontact, the circuit 34 to the relay thereby stopping the selectormechanism of the receiver shunt device 8 from further operation. Therelease of relay again closes at its outer right-hand contact, thecircuit. 31. heretofore mentioned, commonto all of the indicating lightsat the signal punch This last. mentioned circuit, however, is now heldopcn at the outer right-hand contact of relay 25. The operation of relay25 also closes the following circuit: Fromground armature and contact ofrelay 23, conductor 39, contact and armature of relay 25, conductor 40,winding of relay 24 to battery and ground. This will operate the relay24 which will lock up over its left-hand contact and a contact of therelay The operation of relay 25 also closes the circuit over conductor41 tothe relay 42 of the selector potentiometer mechanism 9. This relaywill operate intermittently and move the selector arms around step bystep. This operation of the potentiometer selector mechanism 9 will cutout loss by one-halt transmission unit with each step until the currentthrough the voltmeterrelay 13 again passes the marginal point, thuscausing relay 13 to operate and close its contact 14. Upon thisoperation of relay 13 it will be seen that the circuit previously tracedover contact 14 and conductor 29 is now broken at the right-hand contactand armature of relay 24. The operation opens at contact 15 thepreviously traced circuit to relay 25, thereby causing relay 25 torelease. The release of relay 25 breaks the circuit 41 leading to theselector mechanism 9, thereby stopping the operation of thepotentiometer selector mechanisnrQ. The release of relay 25 at its outerrighthand contact completes again the circuit 3l which is common to allof the indicating lamps of the signal panel. The grounds to theselampsare completed over their respective selector mechanisms, andaccordingly certain of these lights will light, and indicate the loss ofthe circuit or apparatus being measured in transmission units.

When the measurement has been obtained the plug P is withdrawn fromthejack J, thus causing the relay 21 to release. This breaks thepreviously traced circuit to relay 23, allowing it to release, which inturn allows relay 24 to release. The release of relay 21 allowscircuitsto be completed over conductors 45 and 46 to the fourth bank ofselector mechanism 8 and the fourth bank of selector mechanism 9 throughthe windings of relays 26 and 2 As these two last mentioned relays aremeter relay 13, thus preventing another measurement from starting, eventhough the phi; be reinserted into jack J until the outfit has beencompletely restored to normal. \Vhen this occurs, thecontact through thefourth bank .of each of the selectors 8- and 9 has been broken, therelays 26 and 27 then fall back and the circuit is ready for anothermeasurement.

While the invention has been disclosed in certain pecific arrangements'which are deemed desirable, it is understood that it is capable ofembodiment in many and other widely varied forms, without departing fromthespirit of the invention as defined in the appended claims.

What is claimed is:

1. A testing set for determining the transmission characteristics of aline comprising a circuit to which voltage from said line is to beapplied, a responsive device 'in said circuit, means controlled therebyfor automatically introducing steps of loss in said circuit and forsubsequently introducing steps of gain in said circuit until theattenuation of said circuit counteracts the attenuation of said line,

mentioned means for indicating the amount low resistance relays,theselectors step themselves around to normal.

and means controlled by said last\ i l m ssion characteristics of a linecomprising a circuit to which voltage from said line is I to be applied,a voltmeter relay in said circuit, a receiver shunt device forintroducing a step by step loss in said circuit, a potentiometer devicefor decreasing step by step said loss introduced by said receiver shunt,auto- 'matic means for causing the operation ofsaid receiver shunt andthe successive operation of said potentiometer, sa d automatic meansbeing controlled by said voltmeter 16- lay, and means to indicate thedegree of operation of said receiver shunt and said potentiometer.

3. A testing set for. determining the trans mission characteristics of aline comprising a circuit to which voltage from said line is to beapplied, a voltmeter relay in said circuit, a receiver shuntdevice forintroducing a step by step loss in said circuit, said receiver shuntloss for each step being an arbitrarily chosen unit, a potentiometerdevice for decreasing step-by step said loss introduced by said receivershunt, said potentiometer loss matic means' for causing the operation ofsaid receiver shunt and the successive opera-v tion of saidpotentiometer, said automatic means being controlled by said voltmeterrelay, and means to indicate the degree of operation of said receivershunt and said potentiometer.

In testimony whereof, I have signed my name to this specification this8th day of May 1925.-

FRED H. BEST.

